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  • Articles  (28)
  • 1995-1999  (28)
  • Biology  (28)
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  • 1
    ISSN: 1432-0983
    Keywords: Key words Transcriptional regulation ; Phospholipid biosynthesis ; Saccharomyces cerevisiae ; INO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression of structural genes of phospholipid biosynthesis in yeast is mediated by the inositol/choline-responsive element (ICRE). ICRE-dependent gene activation, requiring the regulatory genes INO2 and INO4, is repressed in the presence of the phospholipid precursors inositol and choline. INO2 and, to a less extent, INO4 are positively autoregulated by functional ICRE sequences in the respective upstream regions. However, an INO2 allele devoid of its ICRE functionally complemented an ino2 mutation and completely restored inositol/choline regulation of Ino2p-dependent reporter genes. Low-level expression of INO2 and INO4 genes, each under control of the heterologous MET25 promoter, did not alter the regulatory pattern of target genes. Thus, upstream regions of INO2 and INO4 are not crucial for transcriptional control of ICRE-dependent genes by inositol and choline. Interestingly, over-expression of INO2, but not of INO4, counteracted repression by phospholipid precursors. Possibly, a functional antagonism between INO2 and a negative regulator is the key event responsible for repression or de-repression.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 157 (1997), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this study we show that protein tyrosine kinases and also protein tyrosine phosphatases are involved in the uptake of Listeria monocytogenes by J774 macrophages to a different extent than in the uptake of inert latex beads. In addition, protein tyrosine kinases are necessary for the intracellular growth and survival of L. monocytogenes. The expression of the MAP kinase phosphatase MKP-1, a protein tyrosine phosphatase, is induced upon infection, and phagocytosis of L. monocytogenes by J774 cells overexpressing the MKP-1 protein is reduced compared to control cells. The decreased phagocytosis of L. monocytogenes as a result of the MKP-1 overexpression in J774 macrophages suggests that the activation of the MAP kinase(s) ERK-1 and/or ERK-2 is an essential requirement for the uptake of L. monocytogenes by J774 macrophages.
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we ...
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 20 (1998), S. 0 
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Macrophage cells play a central role during infection with Listeria monocytogenes by both providing a major habitat for bacterial multiplication and presenting bacterial antigens to the immune system. In this study, we investigated the influence of L. monocytogenes infection on the expression of MHC class I and class II genes in two murine macrophage cell lines. Steady-state levels of I-Aβ chain mRNA were decreased in both resting J774A.1 and P388D1 macrophages infected with L. monocytogenes whereas reduction of H-2K mRNA was only observed in P388D1 cells. In addition, L. monocytogenes suppressed induction of MHC class I and class II mRNAs in response to γ-interferon as well as the maintenance of the induced state in activated P388D1 macrophages. Exposure to the non-pathogenic species L. innocua or a deletion mutant of L. monocytogenes, which lacks the lecithinase operon, did not cause a reduction in H-2K and I-Aβ mRNA levels nor suppress expression of Ia antigens. Inhibition of MHC gene expression may represent an important part of the cross-talk between L. monocytogenes and the macrophage that probably influences the efficiency of a T cell-mediated immune response and thus the outcome of a listerial infection.
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the yeast Saccharomyces cerevisiae, growth with a non-fermentable carbon source requires co-ordinate transcriptional activation of gluconeogenic structural genes by an upstream activation site (UAS) element, designated CSRE (carbon source-responsive element). The zinc cluster protein encoded by CAT8 is necessary for transcriptional derepression mediated by a CSRE. Expression of CAT8 as well as transcriptional activation by Cat8p is regulated by the carbon source, requiring a functional Cat1p (= Snf1p) protein kinase. The importance of both regulatory levels was investigated by construction of CAT8 variants with a constitutive transcriptional activation domain (INO2TAD) and/or a carbon source-independent promoter (MET25 ). Whereas a reporter gene driven by a CSRE-dependent synthetic minimal promoter showed a 40-fold derepression with wild-type CAT8, an almost constitutive expression was found with a MET25–CAT8–INO2TAD fusion construct due to a dramatically increased gene activation under conditions of glucose repression. Similar results were obtained with the mRNA of the isocitrate lyase gene ICL1 and at the level of ICL enzyme activity. Taking advantage of a Cat8p size variant, we demonstrate its binding to the CSRE. Our data show that carbon source-dependent transcriptional activation by Cat8p is the most important mechanism affecting the regulated expression of gluconeogenic structural genes.
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Structural genes of phospholipid biosynthesis in the yeast Saccharomyces cerevisiae are activated by the Ino2p/Ino4p transcription factor that binds to ICRE promoter motifs and mediates maximal gene expression in the absence of inositol. We identified the ino80 mutation causing inositol auxotrophy as a result of a defect in ICRE-dependent gene activation. The product of the corresponding wild-type gene INO80 (= YGL150C) shows significant similarity to the Snf2p family of DNA-dependent ATPases. Nevertheless, SNF2 in increased gene dosage did not suppress ino80 mutant phenotypes. Mutation of the Ino80p lysine residue corresponding to the NTP binding site of Snf2p led to a non-functional protein. In ino80 null mutants, gene activation mediated by an ICRE decreased to 16% of the wild-type level. Maximal expression of PHO5, GAL1, CYC1 and ICL1 was also significantly reduced. Thus, Ino80p affects several transcription factors involved in unrelated pathways. As demonstrated by gel filtration, Ino80p is part of a high-molecular-weight complex of more than 1 MDa. Similar to what was found for Snf2p, the Ino80p-containing complex may influence the transcriptional level of several unrelated structural genes by functioning as an ATPase that possibly acts on chromatin.
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ACS1 gene, encoding one out of two acetyl-CoA synthetase isoenzymes of Saccharomyces cerevisiae, is strictly regulated at the transcriptional level by the carbon source of the medium. While ACS1 is poorly expressed in the presence of a high glucose concentration, a several hundred-fold derepression occurs with ethanol as the sole carbon source or under conditions of sugar limitation. The molecular mechanism responsible for the carbon source control of ACS1 turned out to be highly complex. A carbon source-responsive element (CSRE), previously identified upstream of gluconeogenic structural genes, and a binding site of the alcohol dehydrogenase regulator, Adr1p, together mediate about 80% of the derepressed gene activity. Binding of Adr1p synthesized by Escherichia coli to the ACS1 control region was shown by an electrophoretic mobility shift assay. In addition to these activating elements, two URS1 motifs confer negative control on the ACS1 promoter. The URS1 element was found to be a constitutive repression site, which is most effective from a downstream position with respect to an upstream activation site (UAS). In a mutant lacking the URS1-binding factor, Ume6p, ACS1 expression was partially glucose insensitive. Ume6p must counteract transcription factors that are constitutively active. Site-directed mutagenesis of Abf1p binding sites in the ACS1 promoter significantly reduced gene expression in the ume6 mutant, grown under repressing conditions. Thus, a functional balance of the pleiotropic positive factor Abf1p and the negative factor Ume6p is in part responsible for glucose repression of ACS1. The combined influence of the regulated UAS elements, CSRE and Adr1p binding site, mediates a strong increase in ACS1 expression under derepressing conditions.
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  • 8
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; Gluconeogenesis ; Malate synthase ; Transcriptional regulation ; MLS1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The malate synthase gene, MLS1, of the yeast Saccharomyces cerevisiae is transcriptionally regulated by the carbon source in the growth medium. A MLS1-lacZ fusion gene, expressed at a basal level in the presence of 2% glucose, is derepressed more than 100-fold under conditions of sugar limitation. No evidence for MLS1 induction by oleic acid was found. By deletion analysis of the MLS1 control region, we identified two sites, UAS1 and UAS2, as important for efficient derepression of the gene. Both sites contain sequences that resemble the previously characterized carbon source-responsive element (CSRE) found in the promoter of the isocitrate lyase gene ICL1. Indeed, UAS1 and UAS2 in the MLS1 upstream region turn out to be functional CSRE sequence variants. This finding allowed us to define a modified version of the CSRE consensus sequence (CCRTYSRNCCG). Protein binding to UAS1MLS1 was observed with extracts from derepressed but not from repressed cells, and could be competed for by an excess of the unlabelled CSRE(ICL1) sequence. No competition was observed with a mutated CSRE variant. Site-directed mutagenesis of both CSREs in the MLS1 promoter reduced gene activation under derepressing conditions to 20% of the wild-type level. The same decrease was observed with the wild-type MLS1 promoter in a cat8 mutant, lacking an activator of CSRE-dependent transcription. The CSRE/Cat8p-independent activation of MLS1 is mediated by constitutive UAS elements. The pleiotropic transcription factor Abf1p, which binds to the MLS1 upstream region, may contribute to constitutive activation. Thus, in order to ensure the severe glucose repression of MLS1 observed, repressor elements that respond to the carbon source must counteract constitutive activation. In summary, ICL1 and MLS1 share common cis-acting elements, although a distinct mechanism of carbon source control also contributes to MLS1 regulation.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 10 (1997), S. 101-106 
    ISSN: 1432-2145
    Keywords: Key words Pollen ; Pollen competition ; Pollen performance ; Microgametophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We examined the influence of pollen competitive environment on pollen performance in Mirabilis jalapa. We used the number of pollen grains and the number of pollen tubes per pistil as measures of pollen competition. Pollen germination, pollen tube penetration into the style, and pollen tube growth rates were used as measures of pollen performance. All three measures of pollen performance were affected by the competitive environment. Pollen germination was greatest at intermediate pollen load sizes. The percentage of germinated pollen grains that penetrated the stigma and grew into the style decreased with pollen load size. Pollen tube growth rate in the style was greater and more variable with larger numbers of pollen tubes in the style. Controlling for the degree of selection at the stigma indicated that pollen-pollen or pollen-style interactions were the likely causes of increased growth rates.
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  • 10
    ISSN: 1617-4623
    Keywords: Prolidase ; Metalloprotease ; Lactobacillus delbrueckii subsp. lactis ; Nucleotide sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From a genomic library of Lactobacillus delbrueckii subsp. lactis (DSM7290) DNA, in the low-copy-number vector pLG339, a recombinant clone was selected, which complemented a mutation in the prolidase gene (pepQ) of Escherichia coli UK173. Nucleotide sequence analysis revealed an open reading frame of 1104 nucleotides corresponding to a protein of 368 amino acids with a calculated pI of 4.64 and a molecular mass of 41087 Da. The start site of pepQ transcription was determined by primer extension analysis with mRNA prepared from L. delbrueckii. Based on homology of the gene product to various peptidases and on the substrate specificity determined, the peptidase was designated PepQ. The influence of various protease inhibitors and cations on peptidase activity indicated that PepQ is a metalloprotease. The absence of a membrane-spanning domain and a signal peptide sequence argues for a cytoplasmic localization of the enzyme.
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